1. Field of the Invention
This invention relates to paint remover formulations, and more particularly, to formic acid-based compositions which are effective and safe during use.
2. Description of the Prior Art
The term "varnish and paint remover" as applied herein refers to chemical compositions which can strip or facilitate stripping of coatings, such as, paint, varnish, lacquer, shellac, polyurethane finishes and enamels, used to protect substrates such as wood and metal and to beautify them.
Methylene chloride paint strippers are currently the industry standard for stripper performance. Methylene chloride strippers are effective for quickly softening most types of paints. The speed at which methylene chloride performs is believed to be due to its high solvent power coupled with high volatility as reflected by its extremely fast evaporation rate which shortens the work life of methylene chloride paint strippers. Frequently, when methylene chloride paint strippers are used on thick accumulations of paint, more than one application is required since the work life is insufficient to permit penetration through the accumulation of paint.
Suwala, in U.S. Pat. No. 4,812,255 described paint removing compositions which included formic acid and/or acetic acid, N-methyl-2-pyrrolidone (NMP) and an alkylene glycol ether. In the suitable embodiments, the compositions comprised 10 -30% by weight of a mixture of 1 -2 parts formic acid and 3-4 parts acetic acid, 15-40 % by weight of NMP and 40-60% by weight of tripropylene glycol methyl ether (TPM).
Nelson, in U.S. Pat. No. 4,749,510, also described a formic acid-based paint stripping formulation which included 2-15% by weight of formic acid, 20-90% NMP and 30-70% of a 140.degree. F. flash aromatic hydrocarbon solvent, such as Hi Sol.RTM. 15 of the Ashland Chemical Company.
Caster, in U.S. Pat. No. 4,865,758 described a method of removing paint with a lower alkyl substituted 2-oxazolidinone. In comparative results reported therein, it was disclosed that ethyl 3-ethoxypropionate had no effect on paint removal.
McCullins, in British Pat. No. 1,487,737, described a paint remover composition for aerosol type paints in the form of a gel which included methyl ethyl ketone, ethyl acetae, ethoxyethanol and 2-ethoxyethyl acetate. This mixture of solvents was considered effective for paint sprayed graffiti as a viscous, transparent gel containing particles of silica or alumina in suspension.
Palmer, in U.S. Pat. No. 4,120,810, described paint remover compositions of NMP and/or BLO, and at least 35 mole % of blends of alkyl naphthalenes and alkyl benzenes.
These and other compositions, however, have not been particularly effective for removing paint from surfaces without containing objectionable halogenated, aromatic or ether compounds. Furthermore, they do not possess the attributes of being biodegradable, non-flammable, a low vapor pressure and low toxicity.
Accordingly, it is an object of this invention to satisfy the above criteria for an environmentally safe commercial product for removing paint from wood and metal surfaces, and to perform such removal effectively with less material than other related products on the market today.
A particular object of this invention is to provide a paint removal composition in which an activator for acidified NMP is provided which enhances its normally effective action.
Still another object of the invention is to provide a paint stripping formulation which is effective but not overly corrosive so that it can be handled and used easily and safely.
These and other objects and features of the invention will be made apparent from the following more particular description thereof.